1. Field of the Invention
The present invention relates to a scintillator, a radiation detecting apparatus, and a radiation imaging apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2005-214800 relates to mammography which radiographs a breast while sandwiching it. This literature discloses a radiation image sensor including a photosensitive unit having a plurality of photodiodes arranged two-dimensionally and a scintillator layer placed on the photosensitive unit. The scintillator layer has a columnar crystal structure of cesium iodide (CsI) doped with thallium (Tl).
Mammography uses low-energy X-rays exhibiting a large absorption difference between tissues to identify a focus in a breast which is a soft tissue. Combining a molybdenum X-ray tube with a molybdenum filter can generate X-rays similar to monochromatic X-rays including characteristic X-rays. Using such X-rays can obtain an image with high contrast.
In mammography, a breast is placed on a radiographic imaging table incorporating a radiation image sensor and irradiated with X-rays from above while being compressed downward by a compression plate. X-rays are absorbed by the breast, but are not absorbed by any portion other than the breast and strike the scintillator. The X-rays which have struck the scintillator are converted into light by the scintillator. A photodetector placed below the scintillator then photoelectrically converts the light. The output from the photodetector is low in level in the breast region and high in regions other than the breast. This causes halation. The halation influences an image of the breast region in which the output level is low, resulting in white blur and deterioration in contrast. This may lead to inability to perform accurate diagnostic imaging.